Scientists have found out a new treatment for heart attacks – the stem cell therapy. The scientists have observed that the stem cell therapy can partially repair damage of the organ.

The treatment uses heart cells made in the lab from the skin of a genetically matching donor. Tests on monkeys showed that the injections of freshly-made heart cells quickly subsumed into the damaged areas of the heart and helped the organ to pump vigorously. Stem cell trial suggests damaged heart tissue can be regenerated.

However, as a drawback to the research is the fact that the monkeys on whom the procedure was carried out developed unusual heart rhythms, leading the researchers to concede that far more work is needed before the treatment can be considered safe enough for human trials.

One idea scientists have had to treat heart attack survivors is to take skin cells from the patient and convert them into pumping heart cells, hoping that, when injected into the heart, these cells take hold and help the heart pump more effectively. The advantage is that the heart cells will not be rejected by the immune system. But, the procedure is time consuming and expensive to do for individual patients.

Yuji Shiba and others at Shinshu University injected the monkeys with 400m lab-made heart cells and found that they replaced about 16% of the damaged tissue. The new cells were wired up with healthy ones in the heart and over 12 weeks started to help the organ to pump more strongly. Tests revealed, however, that all of the monkeys developed unusual heart rhythms after the therapy. Details appear in the journal Nature.

The scientists are now trying to understand the precise cause of the abnormal heart rhythms, but Shiba told the Guardian: “I think we can manage the post-transplant arrhythmia.”

Sam Boateng, who studies the mechanisms of heart failure at Reading University, said the work was exciting because it was a step towards the possibility of repairing a damaged heart following a heart attack.

“Currently, the only long term option for these patients is heart transplantation, but there are not enough donors to meet the current demand,” he said.

But he added that many challenges remain. “Ideally, immune rejection would be eliminated if the cells could be derived from the same patient, but this is costly and time consuming at a time when the patient requires immediate treatment. Another concern is that the incomplete integration of the transplanted cells could result in irregular heartbeat which can be deadly,” he said.